Fluorodiazadienes and process of making

ABSTRACT

TRIFLUOROMETHYLIMINO TERMINATED COMPOUNDS USEFUL AS DEHYDRATING AGENTS, CROSSLINKING AGENTS AND ULTRAVIOLET LIGHT FILTERS AND PROCESS FOR MAKING BY ISOMERIZING PERFLUORO-A,W-BISAZOMETHINES IN THE PRESENCE OF IONIC FLUORIDE.

United States Patent 3,660,511 FLUORODIAZADIENES AND PROCESS OF MAKINGPaul H. Ogden, Oakdale Township, Minn., assignor to Minnesota Mining andManufacturing Company, St.

Paul, Minn.

No Drawing. Continuation-impart of application Ser. No. 577,192, Sept.6, 1966. This application Apr. 3, 1967, Ser. No. 627,607

Int. Cl. C07c 119/00 U.S. Cl. 260-566 R 14 Claims ABSTRACT OF THEDISCLOSURE Trifluoromethylimino terminated compounds useful asdehydrating agents, crosslinking agents and ultraviolet light filtersand process for making by isomerizing perfluoro-a,w-bisazomethines inthe presence of ionic fluoride.

CROSS REFERENCES This application is a continuation-in-part of myearlier filed application Ser. No. 577,192, now abandoned.

My copending application, U.S. patent application Ser. No. 562,540 tiledJuly 5, 1966 now Pat. No. 3,374,581, teaches starting materials usefulin the practice of this invention.

BACKGROUND Partially fluorinated carbodiimides, e.g.

CF N=C=NCH have been reported previously, see S. P. Markarov et al.,Dokl. Akad. SSSR, 142, 576-9 (1962), but the process known for preparingsuch compounds is not applicable to completely fluorinated materials.The above cited reference discloses the preparation of CF N= C,=NCH bymeans of thermal decomposition of a compound having the structureCH3N-CC=NOH3 NC F This process as well as its product are substantiallydissimilar to the present invention.

Few methods of preparing perfiuoroazaalkenes have been reported in thechemical literature. Those processes which have been reported, such asthe pyrolysis of polyfiuorooxazetidenes (R. N. Haszeldine et al., J.Chem. Soc., 1351 (1961) and references therein) or perfluoro tertamines(W. H. Pearlson and L. J. Hals, U.S. Pat. 2,643,267), are applicableonly to the preparation of monoazaalkenes.

One reported preparation of difnnctional perfluoroazaalkenes involvesthe photolysis of tetrafluoro-2,3-diazabutadiene, CF =NN=CF in thepresence of fluoroolefins (P. H. Ogden, US. patent application Ser. No.562,540). Azaalkenes prepared by this process possess the generalstructure CF =N-R N=CF where Rf is a perfluoroalkylene group.

Perfluoroazines, characterized by the functional group -CF=NN=CF-, havebeen reported (W. 'F. Chamhers, US. Pat. 3,117,996). Perfluoroimines,characterized by the functional group C=NF (R. A. Mitsch, J. Am.

3,660,511 Patented May 2, 1972 isomerize readily in the presence ofionic fluoride to produce compounds having the characteristicsubstituent p.

This novel process has led to a route to certain novel compounds of thisinvention from the novel difunctional starting materials described bythe inventor in the previously cited copending application. No routepreviously known to the inventor teaches the novel difunctionalcompounds of this invention.

SUMMARY It has now been discovered that trifluoromethylimino terminatedcompounds of the general formulas:

where, in each formula, X and Y are fluorine or a lower perfluoroalkylgroup, n is an integer of from 0 through 20 inclusive, and m is aninteger from 0 through 10 inclusive, are prepared by contacting underanhydrous conditions, with ionic fluoride, perfluorodiazadienes of theformulas:

where X, Y and n and m are as defined above.

The ionic fluoride may be supplied by the compounds of Formulas 6through 9 themselves (when eg Water is present) or by adding a suitablesource of ionic fluoride, preferably cesium fluoride. The desiredtrifluoromethylimino terminated products of Formulas 1 through 5 arethen formed as a result of isomerization induced by ionic fluoride.

The isomerization reaction of this invention requires a condensed phase,that is, either a solid ionic fluoride phase with the azomethine presentas vapor or liquid, or a homogeneous liquid phase containing fluorideion in solution. The term ionic fluoride therefore includes both solidsalt-like structures and free fluoride ion. Compounds in which thefluorine appears as a stable complex, e.g. ferric fluoride, aregenerally not suitable. Compounds which readily produce fluoride ionupon hydrolysis by adventitious moisture such as SiF can be used ascatalysts, but the resulting low fluoride ion concentration results inslow and incomplete isomerization. The preferred isomerization catalystsare the alkali metal fluorides, particularly cesium fluoride. The totalamount of fluoride present in a reaction zone does not control thereaction. The rate of reaction depends upon the amount of surfaceavailable where a solid phase is present. In the case of the homogeneousreaction the rate is appatently proportional to the concentration offluoride ion in the liquid phase.

The azomethine starting material may be present as liquid or vapor ormay be in solution, preferably in an inert organic solvent, e.g. asolvent which does not itself appreciably react with the azomethineunder the condi tions of the reaction and preferably does not react withthe desired products. Such solvents are free of active Zerewitinoffhydrogen and dissolve, under the reaction conditions, at least 1% byweight of the azomethine. Such solvents include halocarbons, such asCFC13, HCF CI, oxygenated organic compounds, such as acetone, ethylacetate, and the like.

The reaction is preferably carried out at room temperature, but it willproceed within a temperature range of C. to 150 C. The reaction rate isincreased when the reaction temperature is increased for a given ionicfluoride concentration.

The reaction which takes place is an isomerization which may berepresented by the following equation:

6 CF=NCFX-CFYN=CF2 CFaN=OX-CYNCFa where X and Y are each as definedabove. The rate of isomerization varies according to the source of ionicfluoirde used; thus, in the presence of cesium fluoride, perfluoro (3-methyl-2,5 -diazahexa- 1,5 -diene is completely converted intoperfluoro(3-methyl-2,5-diazahexa 2,4 diene), CF -N=CFC-(CF )=N-OF while,in the presence of traces of fluoride ion from silicon tetrafluoride orhydrogen fluoride obtained, for example, through the admission of tracesof water into the apparatus, CF ==N--CF -CF(CF )N=CF is converted onlyto the half isomerized perfluoro(3-methyl 2,5-diazahexa 1,4 diene), CFN=CF*CF(CF )N=CF after sixteen days.

Usually conversion from the perfluoro 0:,w bisazomethine is complete inthe presence of cesium fluoride and no purification of products isnecessary; however, the boiling points of starting material andisomerized product are usually sufficiently different to enableseparation to be accomplished if necessary, e.g.

boils at 43 C. whereas its isomer CF N=C=N-CF boils at 7 C.

The starting compounds of Formulas 6 through 9 are prepared by theultraviolet photolysis of a mixture of perfluoro-2,3-diazabuta-1,3-dienewith a fluorinated olefin at a temperature in the range of l40 to 100C., as described in my copending U.S. patent application No. 562,540 nowPat. No. 3,374,581.

The compound of Formula 1, which is herein termed bis(trifluoromethyl)carbodiimide, and the compounds of Formulas 2 through 5, which areherein termed perfluorodiazadienes, are useful dehydrating agents asexemplified by their use in the preparation of esters from acids andalcohols. The compounds abstract water from the reacting species and areconverted into ureas, oxamides or a-keto-amides. They are thus useful inthat they can be used in a fiuorinated system with which non-fluorinateddehydrating agents are incompatible. Especially useful in this respectis bis(trifiuoromethyl) carbodiimide.

In general, the compounds of Formula 2 are useful as ultraviolet lightfilters in the range from about 180 to 200 Inn.

The compounds of Formulas 1 through 5 are useful as cross-linkingagents. Thus, such products are admixed with prepolymers which containactive hydrogen atoms, such as polyalcohols, including polyvinylalcohol, or polyamides, including polycaprolactam, and the like under adry atmosphere, then treated with Water to produce diester or diamidecrosslinks.

Compounds of Formulas 4 and 5 are useful for the preparation ofdicarboxylic acids and amides.

Compounds of Formulas 1 and 2 are useful intermediates for themanufacture of fluorinated amides as taught, for example, in mycopending US. patent application Ser. No. 627,609 filed on even dateherewith now Pat. No. 3,538,157.

The carbodiimide of Formula .1 is a volatile liquid which boils at 7 C.It can be separated from its starting materials, solvent and by-productsby conventional methods such as vapor phase chromatography, fractionaldisdilation-condensation or fractional distillation. It is readilyhydrolyzed by water, and care must be taken to exclude traces ofmoisture from the apparatus in which it is handled.

The perfluorodiazadienes of Formulas 2 and 3, range from colorlessliquids to white solids, the higher molecular weight compounds generallyhaving the higher melting points. They are readily hydrolyzed and caremust be taken when handling them to exclude moisture from the apparatuswhich is used.

EXAMPLES The following examples more particularly illustrate theinvention: i

EXAMPLE '1 (A) Preparation of the starting material Perfiuoro2,3-diazabuta-l,3-diene, CF =N-'N==CF (30 millimoles) is condensed at19-6 C. under vacuum into a silica tube of 200 ml. capacity, fitted witha polytetrafiuoroethylene valve. The tube is sealed, and, after warmingto room temperature, the contents are irradiated for 1-6 hours withultraviolet light from a 1000 watt, air cooled ultraviolet lamp (anelectric lamp producing strong ultraviolet light in the region of1800-4000 A. and available from the General Electric Company under thetrade designation EH6 is suitable).

The contents of the tube are then pumped under vacuum into a trap cooledto -196 C. and subsequently characterized, by infrared, F N.M.R. andmass spectra, together with elemental analysis, asperfluoro-2,4-diazapenta-1,4-dicne, CFFNCF N=OF (20 millimoles 100%conversion) and nitrogen.

(B) Preparation of bistrifiuoromethyl carbodiimide Ten millimoles ofperfluoro-2,4-diazapenta-1,4-diene, C F ==NCF -N=CF are condensed into atube containing 0.1 g. of dried cesium fluoride. After remaining for twohours at room temperature, the volatile material is removed from thetube and separated into its components by vapor phase chromatography.The major component is found to be bis(trifluoromethyl) carbodiimidehaving the structural formula CF -N=C,-=N-CF the retention time ofwhich, relative to chlorotrifluoromethane, is 21.0. The yield approachestheoretical with recovery of product (about 8 millimoles) being inexcess of percent.

The product, which boils at about 7 C. under normal pressures, hascharacteristic spectra. Thus, it shows a strong infrared absorption at22.10 cm.- corresponding to the N=C=N group, a single peak in the Fspectra at 50.2 corresponding to the CF;, group, and its molecularweight is found to be 1 80 (C N F requires 178) when determined byeifusion techniques using a mass spectrometer as an eflusiometer.Analysis, calculated for C F -N F, 64.0; found: F, 63.5.

EXAMPLE 2 Perlluoro 2,5-diazahexa-1,5-diene,

(0.1 g.) is condensed in vacuum into a Pyrex tube containing cesiumfluoride 0.1 g.) and malntamed at room temperature for twelve hours.Perfluoro 2,5-diaaahexa- 2,4-diene, CF --N=CF-CF=N--CF is obtained 1nquantitative yield and characterized by its F N.M.R., infrared and massspectra together with molecular weight. Its F N.M.R. spectrum indicatestwodiiferent types of fluorine atoms in the ratio of 3:1, the infraredspectrum shows a strong absorption at 1750 cm? corresponding to the G Nbond and the mass spectrum shows a parent peak at m/e=228 which gave amolecular weight by effusion of 231 (Th. 228).

(III) in the ratio of about 5:1. When this material is allowed to standover cesium fluoride it isomerizes completely to (HI) within thirtyminutes. (H) and (IH) are identified by their infrared mass and F N.M.R.spectra together with molecular weights.

(II) Infrared, 1802, 1770 cm.- -corresponding to F N.M.R. indicates sixdifferent types of fluorine atom in the ratio 3:3:1:1:1:1 and four ofthe peaks are each accompanied by a smaller peak corresponding to thegeometric isomer, mass spectrum shows a parent ion at m/e=278 themolecular weight of which is found to be 278 by effusion.

(III) Infrared 1770, 1712 cm. corresponding to F N.M.R. shows fourdifferent types of fluorine atoms in the ratio 3:3:3zl, each peak beingaccompanied by a smaller one corresponding to the geometric isomer. Themass spectrum shows a parent ion at m/e=278.

EXAMPLE 4 Perfluoro (3,4-dimethyl-2,5-diazahexa-1,5-diene) CF FNCF CF 3)CF (CF N=CF (0.1 g.) and CFCl is condensed into an N.M.R. specimentube, containing cesium fluoride (0.1 g), which is then sealed. After 12hours at ambient temperatures the material has isomerized to yieldperfluoro(3,4-dimethyl- 2,5 -diazaheXa-2,4-diene) which is identified byits F N.M.R. and mass spectra. F N.M.R. shows two different types offluorine at the ratio 1:1. The yield is 65%.

EXAMPLE 5 Perfluoro-2,5-diazahexa-2,4-diene (0.1 g.) is condensed into aflask together with water (2 cc.). After standing for 1 day, whiteneedles are obtained which are identified by infrared spectrum as N,N'bis(trifluoromethyl)oxamide, CF NHCOCONHCF EXAMPLE 6 A sample ofperfluoro a,w-bisazomethine of the general Formula CF =N(CF N=CF isprepared by photolyzing a mixture of tetrafluoro-2,3 diazabuta- 1,3-diene (1 part) and tetrafluoroethylene (10 parts) m a silica ampoule.The solid product is then dissolved m chlorotrifluoromethane andtransferred to a flask contaming dried cesium fluoride. The terminalazomethine group is shown by infrared spectral measurements, to haveisomerized producing an N-trifluoromethyl terminated compound of thestructure CF N=CF(CF ),,CF=NCF EXAMPLE 7 The procedure of Example 6 isrepeated using the compound prepared from tetrafluoro 2,3 diazabuta-1,3-diene and chlorotrifluoroethylene. A compound which possesses thegeneral formula where m is as defined above is obtained.

The product obtained in this case-is identified as having the structureCF -N=CF(OF CFCl) CF=N-CF where m is as defined above by infraredspectral measurements.

I claim:

1. A compound having the formula where X and Y are each fluorine or alower perfluoroalkyl group.

2. A compound having the formula where X is fluorine or a lowerperfluoroalkyl group.

3. A compound having the formula where n is an integer of from zero to20, inclusive.

4. A compound having the formula where m is an integer from zero through10, inclusive 5. Perfluoro-Z,5-diazahexa-2,4-diene.

6. Perfluoro 3-methyl-2,5-diazahexa-2,4-diene) 7. Perfluoro(3-rnethyl-2,5-diazahexa-1,4-diene) 8.Perfluoro(3,4-dimethyl-2,'5-diazahexa-2,4-diene).

9. Perfluoro(2,5-diazahexa-1,4-diene).

10. A process for the preparation of fluorinated diazadienes whichcomprises contacting under anhydrous conditions a fluorinateda,w-bis(azomethino) alkylene with alkali metal fluordie as a source offluoride ions at a temperature ranging from about 0 to C., said alkylenebeing selected from the group consisting of:

14. The process of claim 13 wherein the solvent ischlorotrifluoromethane.

(References on following page) References Cited UNITED STATES PATENTS10/1964 Heberling 260288 5/1967 Schlack et a1. 260-551 OTHER REFERENCESYale, J. Med. and Pharm. Chem, vol. 1 (2), pp. 121- 33 (1959).

Chambers et al., J. Am. Chem. Soc., 'vol. 84, pp. 2337- 10 8 Banks, J.Chem. Soc., pp. 7207 and 7209 (1965). Barr, J. Chem. S0c., pp. 2532 and2533 (1965). Markarov et al., Chem. A-bst, vol. 57, col. 4528 (d),

Bacharov, Russ. Chem. Revs, v01. 34 (3), p. 216

LEON ZITVER, Primary Examiner G. A. SCHWARTZ, Assistant Examiner US. Cl.X.R.

26078 SC, 91.3 VA

Patent No. 3,660,511 Dated May 2, 1972 Inventor(s) PAUL H OGDEN It iscertified that error appears in the above-identified patent and thatsaid Letters Patent are hereby corrected as shown below:

Column 2, Line 33, should read (1) CF3-N=C=N-CF3 Column 3, Line 3 theformula at the end of the line should read Column 5, Line 3, "C F N :F"should read Signed and sealed this 29th day of August 1972.

(SEAL) Attest:

EDWARD M.FLETCHER,JR. ROBERT GOITSCHALK Attesting Officer Commissionerof Patents FORM PC4050 (10459) uscoMM-Dc 60376-P69 I U.51 GOVERNMENTPRINTING OFFICE Z 969 0-355'334

